With expanding utilization of radioactive materials, in the medical, scientific, and industrial fields and the like, there is continuing need for improved equipment for detecting and monitoring radiation emanating from such materials.
Radiation is a potential health hazard, therefore, maximum permissible levels of exposure by humans to radiation are established by various commissions and Governmental regulations. It is thus necessary to monitor areas of potentially high radiation levels to avoid undue exposure. Also, the detection of radiation can be a valuable aid to monitoring the operation of equipment containing radioactive material. For example, an increase in the detected radiation level in the environment adjacent a system containing radioactive materials may indicate leakage from the system before such leakage can be detected by other means.
An example of industrial use of radioactive material is a nuclear reactor power plant. In the water-cooled version of a nuclear reactor in common use, water is heated by passage through a core of nuclear fuel contained in a pressure vessel and steam thus produced is applied to a turbine-generator to produce electrical power. The pressure vessel is contained in a thick-walled cavity or "dry-well" which in turn is surrounded by a containment building. Such nuclear reactor systems are discussed, for example, by M. M. El-Wakil in "Nuclear Power Engineering", McGraw-Hill Book Company, 1962.
In such nuclear reactor plants there are many areas where radiation monitoring is desired and/or required, for example, in the dry-well, in areas occupied by humans for operation or maintenance, in ventilation and off-gas ducts or stacks.
There are a number of types of radiation including gamma rays and alpha and beta particles. Such radiation is potentially harmful to living matter because of its capability of ionizing such matter. The damaging effect of radiation depends on many factors including the type, energy and time distribution of the energy. Thus there are several aspects of radiation of potential interest. One aspect of radiation is the number of radiation events or particles per unit time. Another aspect of radiation is the energy of the radiation either cumulatively or as a rate. A related aspect is the relative biological effectiveness (i.e. the effect on living tissue) of the radiation. The relative biological effectiveness is the ratio of the biological dose (expressed in units called rems) to the energy absorbed per gram of tissue (expressed in units called rads--one rad being equal to 100 ergs per gram).
Various devices for detecting radiation and measuring the various aspects thereof, such as count rate, dose rate, pulse height distribution, etc., are known as discussed, for example, by W. J. Price in "Nuclear Radiation Detection", McGraw-Hill Book Company, 1964.
However, particularly for monitoring radiation in systems such as nuclear power plants, there is a continuing need for a radiation monitor which will detect radiation and directly provide simultaneous measurements of the dose rate, concentration and average energy of the radiation from the atmosphere being monitored.
Thus an object of the invention is to provide an improved radiation monitor.
Another object of the invention is a radiation monitor providing indications of the dose rate, concentration and energy of radiation detected by a single radiation detector.